This invention relates to a method of producing steel slabs. More particularly, it relates to such a method in which the slabs are rolled from an ingot poured in a member of the group of molds consisting of open-top and hot-top molds.
Slabs of steel are ordered on the basis of metallurgical grade, maximum weight, and specified width. According to the metallurgical grade, the steel is poured either into a bottle-cap ingot mold, which is characterized by a fixed volume, or into either an open-top or a hot-top ingot mold, which has a variable volume.
In the past, open-top and hot-top ingots were somewhat arbitrarily assigned a maximum providing yield of 94% and 86%, respectively. This percentage was based upon the maximum yield from the highest yielding ingot size. Thus, to determine the proper size ingot mold and pour height for a particular slab, a data base was first searched to obtain the smallest open-top, or hot-top, depending on the grade ordered, ingot mold in stock that would produce an ingot: (1) having one cross-sectional dimension larger than the sum of said specified width plus the width increment reserved for edge work, and (2) a full mold ingot weight greater than the ordered maximum slab weight.
The ordered maximum slab weight was then divided by the maximum providing yield to obtain the required ingot weight. Ingot weight tables, containing ingot weight versus pour height, were then consulted to obtain the required pour height.
It has been found that the yield from open-top and hot-top ingots varies by as much as 10%, depending upon the ingot size, the pour height, and the slab width. Thus, using the prior art method of determining ingot size and pour height generally resulted in slabs that were lighter than the desired weight.
It is an object of the present invention to provide a method of producing a slab of steel from an open-top or hot-top ingot in which the actual weight of the slab is about equal to the ordered maximum weight of the slab.